EPROMs find a wide range of usage in the newer telephone switching systems and are usually set in a factory prior to assembly into a switching machine. Each EPROM is characterized in the ability to be erased by subjection of the memory sites to ultraviolet light which acts to erase or set all of the sites to an "all-ones" state. The programming of such a memory is accomplished by selectively switching or resetting various permutations of bit locations in each memory site to the zero condition to provide the required data storage. Heretofore, the programming of the memory sites has been generally attained by programming the EPROMs on an individual basis, that is, each EPROM is separately programmed in accordance with data received from a single program source.
In programming EPROMs, situations often arise where the byte to be programmed at a memory site consists of "all-ones" data. Significant time is consumed in routing and impressing each bit into a memory location, and manifestly it is a wasteful operation to route an "all-ones" byte into a site that is already set in an "all-ones" condition. This situation is quite common because the source program data comprises many bytes of "all-ones " which may be indicative of intelligent (real) data, a space, or, one or more sites to be reserved for future programming. It is believed apparent that it is desirable to have a system which is capable of simultaneously programming a number of EPROMs together with facilities for avoiding the programming of bytes of "all-ones" where the intended memory sites are already in an "all-ones" condition.